The present invention relates to a grease supply confirming device and method which can be applied to bearings for use in, e.g., spindle for machine tools that are required to operate at a high rotary speed and have a prolonged life.
Most bearings for the spindle for machine tools and bearings for spindle devices are grease-lubricated for cost reduction or omission of maintenance. In order to meet the requirements for higher productivity, the spindle of machine tools must operate at higher rotary speed. Thus, these bearings have been required to operate at higher rotary speed.
The upper limit of rotary speed of grease-lubricated rolling bearing devices is dmN1,500,000 (dm: pitch diameter (mm); N: shaft rotary speed (rpm)) at maximum.
In order to prevent seizing of bearings, it has been proposed to use a grease supplying device.
In the case where such a grease supplying device is used, it is important to confirm to see whether or not a semi-solid grease is normally supplied into the bearing. This is because the semi-solid grease can block the pipe, preventing the supply of the grease into the bearing. In the case where the bearing operates at a rotary speed as high as greater than dmN 1,500,000, the grease is scattered and then makes little contribution to lubrication. Thus, when the bearing continues to operate at a high rotary speed without the supply of grease, the grease is deteriorated, causing the seizing of the bearing soon.
In order to detect abnormalities such as suspension of grease supply, Japanese Patent Laid-Open No. 1999-93957 discloses a technique involving the use of a piping which is partly transparent so that the flow of grease to be supplied into the bearing can be visually monitored.
In practice, it has been difficult to monitor visually the bearing of spindle for machine tool which operates continuously for a long period of time for the state of grease supply because cost, including labor cost, rises. In actuality, the state of grease supply can be visually confirmed only several times a day, making it impossible to early detect abnormalities such as suspension of supply of grease by the supplier. It has been still disadvantageous in that when the machine tools operate at a rotary speed as high as greater than dmN 1,500,000, the bearing undergoes seizing, making the spindle out of order.